Quick Answer
The answer is to cache the data key locally and reuse it for multiple items. This is correct because client-side encryption with DynamoDB typically requires a call to the KMS GenerateDataKey API to obtain a data key for each write operation, and each API call introduces network round-trip latency. By caching that data key and reusing it across multiple items, you eliminate repeated KMS calls, directly reducing DynamoDB client-side encryption latency via KMS key caching. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of performance optimization within the client-side encryption pattern—a common trap is assuming you must call KMS for every item, but the SDK supports key caching natively. Remember the memory tip: “One key, many writes—cache to avoid the KMS plights.”
This SCS-C02 practice question tests your understanding of data protection. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses Amazon DynamoDB with client-side encryption using AWS KMS. The application is experiencing high latency on write operations. Which change is most likely to reduce latency?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Switch to server-side encryption with KMS
Why wrong: Still requires KMS calls for encryption.
Increase the provisioned write capacity of the table
Why wrong: Addresses throughput, not encryption latency.
Use DynamoDB Accelerator (DAX)
Why wrong: DAX caches data, not encryption keys.
Cache the data key locally and reuse it for multiple items
Reduces KMS API calls.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Cache the data key locally and reuse it for multiple items
Option D is correct because client-side encryption with AWS KMS typically involves calling the KMS GenerateDataKey API to obtain a data key, which is then used to encrypt items locally. Each KMS API call adds network latency. By caching the data key locally and reusing it for multiple items, you eliminate repeated KMS round trips, significantly reducing per-write latency. This is a well-known optimization for client-side encryption patterns.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Switch to server-side encryption with KMS
Why it's wrong here
Still requires KMS calls for encryption.
Increase the provisioned write capacity of the table
Why it's wrong here
Addresses throughput, not encryption latency.
Use DynamoDB Accelerator (DAX)
Why it's wrong here
DAX caches data, not encryption keys.
Cache the data key locally and reuse it for multiple items
Why this is correct
Reduces KMS API calls.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse throughput capacity (Option B) with latency, or assume DAX (Option C) can accelerate writes, when in fact DAX only caches reads and does not affect write path latency.
Detailed technical explanation
When using client-side encryption with KMS, the application calls GenerateDataKey to get a plaintext data key and an encrypted copy. The plaintext key is used to encrypt items locally, and the encrypted key is stored with the item. Each write that requires a new data key triggers a KMS API call, which typically adds 5–10 ms of latency per call. Caching the data key in memory for a configurable TTL (e.g., 5 minutes) avoids these calls for subsequent writes, reducing per-item latency to the local encryption time only. This pattern is documented in the AWS Encryption SDK and is a standard performance optimization.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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FAQ
Data Protection — This question tests Data Protection — Read the scenario before looking for a memorised answer..
The correct answer is: Cache the data key locally and reuse it for multiple items — Option D is correct because client-side encryption with AWS KMS typically involves calling the KMS GenerateDataKey API to obtain a data key, which is then used to encrypt items locally. Each KMS API call adds network latency. By caching the data key locally and reusing it for multiple items, you eliminate repeated KMS round trips, significantly reducing per-write latency. This is a well-known optimization for client-side encryption patterns.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
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